In the article “ECG-correlated image reconstruction from subsecond multi-slice spiral CT scans of the heart” M. Kachelrieβ, S. Ulzheimer, and W. A. Kalender, Med. Phys. 27, 1881-1902, 2000 a computed tomography apparatus for acquiring projection data of a heart of a human being is disclosed, wherein an electrocardiogram is measured simultaneously such that the projection data can be assigned to different cardiac phases, i.e. to different moving phases of the heart. The projection data assigned to different moving phases are used for reconstructing an image of the heart, which shows the heart in the different moving phases, i.e. for each of the moving phases a three-dimensional image of the heart is reconstructed and these three-dimensional images are combined to a four-dimensional image showing the heart in different moving phases.
In order to reconstruct a three-dimensional image of the heart in different moving phases, for each moving phase projection data have to be acquired, which preferably fulfill the so-called sufficiency condition, i.e. each point of the heart, which has to be reconstructed, has to see the radiation source over an angular range of at least 180°. In order to fulfill the sufficiency condition for each point of the heart, which has to be reconstructed, and for each moving phase, a relatively large amount of projection data has to be acquired, which leads to a relative high radiation dose applied to the human being.